Regarding the solid content of the slurry

On the outside of the curve. Impeller and guide vane of the slurry pump.

The solid content of the slurry is between 10 and 15, which is indeed high. It is recommended to conduct more thorough inspections at pipeline elbows, valve bodies, heat exchangers, etc., and to perform regular thickness measurements. The valves in the slurry system should be kept in the fully open position to prevent wear on the valve plates. Furthermore, it is crucial to identify the reason for the high solid content. If the fine particulate content in the three-spin system is normal, then there is a problem with the lift pipe and the settler. One must not be careless.

My plant has encountered this issue as well; just a few days ago, we sent personnel to conduct regular inspections of the slurry system. In the past, my plant had to shut down due to pump wear caused by high solid content. It was high this time as well, but after some adjustments, it is now kept below 1, by using the method of multiple oil slurry discharges. It is quite effective; if the pump operates for a long time, pay more attention to it, but the pipelines generally won’t have any problems.

It is unknown whether the regenerator is burned out (issues such as the degree of catalyst breakdown), whether there are problems with the reactor’s rapid separation equipment, and whether the slurry is regularly removed, especially when dealing with heavy feedstocks. All of these can result in a higher solid content in the slurry.

The mechanical seal of the slurry pump may leak due to wear. Once, in our plant, a high solid content in the catalytic slurry caused damage to the mechanical seal of the slurry pump, which led to a fire. Therefore, a high solid content in the slurry cannot be taken lightly; it is necessary to identify the cause as soon as possible. The problem is likely related to the equipment itself, such as cracks in the welds of the cyclone, material degradation, or coking of the flap valves.

A high solid content in the slurry is indeed very dangerous. The pump casing of our slurry pump was once worn through; fortunately, it was detected in time, and an emergency shutdown prevented a fire from occurring. During the shutdown inspection, it was found that the wing valves of the secondary centrifuge in the settler were clogged due to carbonization. Operating with a solid content of over 10 for 2 months is quite dangerous; it is necessary to strengthen inspections in order to detect problems promptly. It is best to shut down for maintenance.

Pay special attention to the outside of the elbows; it’s better to use ceramic in slurry pumps. Also, the control valves for the upward and downward flow within the tower are those that tend to wear out most easily. Check more often, measure the thickness. There is sludge; reducing the amount of heavy recycle can help, so discard more sludge. The best thing is to find out the cause. We’ve been running it for over a year and it’s still fine.

It’s a bit too high; could it be due to catalyst loss? It’s necessary to find out the cause as soon as possible

The catalyst loss is quite severe, right? During maintenance, check the cyclone separator – there might be a problem there

At levels of 10–15 g/l, it’s generally not a big problem; usually we keep it below 6 g/l. Wear and tear becomes more severe once the level exceeds 50. The wear and tear isn’t that severe, right? If it wears out on both sides, it’s a problem with the catalyst breaking down. Unilaterally, it could be a problem with the centrifuge.

Ha, we can’t jump to conclusions so easily! Our method for analyzing the solid content in oil slurry is centrifugation. We focus on this solid content primarily to determine whether there is catalyst fine powder present. However, due to the differences in the raw materials processed by the facility, the gel content in the oil slurry varies; as a result, these gels can only be simply considered as solids (catalyst) when using the centrifugation method to measure solid content. But in reality, they cannot be used as a criterion for determining runner failure in settlers. Therefore, further washing with organic solvents is possible; thus, we defined the solid content before washing and the solid content after washing for the oil slurry. As data for the comprehensive evaluation of the slurry condition. Generally, if the solid content after washing is still less than 1.6 g/l, the situation isn’t that serious. But after all, gel is also a product resulting from the tendency to coking. Therefore, it is recommended to ensure an adequate external discharge volume and keep the bottom temperature of the fractionation tower at a lower level. As long as there is no leakage from the settler and the operating conditions are well controlled, there should be no problems over a long period of time. For reference only; it’s not necessarily entirely correct.

If the level remains low during operation, but the solid content of the slurry exceeds the specified limit after running for a while, it is generally assumed that coking in the cyclone separator is the cause! Be extremely careful once the solid content of the slurry exceeds the limit! Strengthen inspections, paying special attention to the slurry pump, the outside of the outlet elbow, the pre-heating line, etc. In situations where there’s no other solution, I’ve had to cover them with boxes as a makeshift fix! Of course, attention must also be paid to each slurry heat exchanger; in such conditions, the inlet and outlet valves as well as the bypass lines need to be operated frequently, as they are prone to clogging! In terms of operation, the following points should be noted: 1. Closely monitor whether the solid content of the slurry deteriorates; if this occurs, shut down the process immediately, otherwise a large amount of catalyst will end up in the distillation tower! 2. Closely monitor the viscosity and circulation volume of the slurry; if the viscosity is too high or the circulation volume decreases, it is necessary to increase the external discharge promptly, reduce the reaction depth, send more reprocessed oil back to the fractionating tower, and improve the properties of the slurry. 4. At this time, it is best not to reprocess the slurry oil to avoid wearing out the nozzle. 3. Develop emergency plans for oil slurry leaks and emergency shutdowns as early as possible, and make preparations in advance! ! ! ! Of course, I have also encountered situations where the high solid content is caused by the raw materials; if it is indeed the raw materials that result in a high solid content in the slurry, this can be determined through testing! Place the final solid remaining from the oil slurry’s solid content in a crucible and burn it; if it burns completely, it is due to the properties of the raw material ； If it turns into a white powder after burning, it must be fine catalyst powder! In short, whatever the reason for the high solid content in the slurry, it should be given serious attention, and measures should be taken to resolve it promptly to avoid accidents! !

It’s almost certain that there’s a problem with the settler.

1. Impeller retaining ring of the slurry pump 2. Preheating element of the slurry pump 3. Thinning section at the inlet of the slurry pump 4. Prone to clogging in the slurry cooler. These are issues we encountered in our facility previously; hope this helps.

The solid content in the slurry is generally required to be no more than 10 grams; the amount mentioned by the original poster has little impact on operations, but it should still be taken seriously. It is necessary to check whether the reaction is normal and whether the catalyst fine powder level is too high. so that measures can be taken in a timely manner. The impact on operation is mainly wear of the pump ring and impeller in the slurry system, as well as wear of the valve discs in the slurry system, resulting in poor sealing. In severe cases, it can also cause blockage of the heat exchanger tube bundle.

1 Coking and blockage may occur at the bottom of the distillation tower. 2 Elbows for the pipeline. 3 Pump inlet filter screen. 4 Slurry heat exchanger. Preheater for pump 5. 6 Pipeline control valves – these are all points that need attention; it’s best to find out the reason for leakage in the settler.

Our unit also has a relatively high solid content, and a few days ago there was an incident in which the valve on the pre-heating line was worn through, causing oil slurry to be sprayed out.

Oh! It’s similar to the current state of our equipment. However, after thorough investigation, we found that the solid content consists entirely of fine powder – something that didn’t happen before. Why is there so much fine powder now? We are still investigating this, and I hope those who know the reason can explain it to me. Thank you in advance

It’s too high; theoretically, it should not be greater than 6, and ours should not exceed 4. 1. It can easily wear out the pump seals, leading to leaks and fires. 2. The pipelines are prone to clogging. 3. The trays in the distillation tower cannot handle this either; they get clogged easily. 4. The temperature of the slurry is very high, so heat exchange with other materials is necessary, and the heat exchange equipment tends to get clogged easily

The solid content of the slurry is 10, which is not too high; it’s important to maintain stable control of the reaction pressure, but there shouldn’t be any major issues. Prone to wear: 1. Slurry casing and impeller. 2. Elbow. 3. Valves or control valves used to regulate flow – in our case, the valve cores wore out and were destroyed. 4. The nozzle for re-refining oil slurry is also prone to wear.